Section switches have little or no circuit-breaking ability. Nevertheless, it is desirable for section switches to have some circuit-breaking ability, in order to perform certain loop transfer operations.
An object of the present invention is to provide a section switch with considerable circuit-breaking ability, e.g. enabling 4200 A at 20 kV phase-to-ground to be interrupted.
Another object of the invention is to provide a section switch capable of operating safely even if ice has formed on the apparatus, without penalizing the cost price of the apparatus by providing an overdimensioned drive mechanism.
U.S. Pat. No. 2 897 323 describes an apparatus combining a section switch and a circuit breaker, in which, on opening, current is deflected via an arcing horn that cooperates with a small wheel. That apparatus cannot operate when ice has formed on the arcing horn and on the wheel since the mechanism operates in compression. A much higher force is required to break ice in compression.
Another object of the invention is to provide a section switch in which ice is broken without using a large force.
U.S. Pat. No. 2 824 936 proposes placing the blade of a section switch in such a manner that contact with the arcing horn takes place laterally. The Applicant has observed that if a large force is exerted on the blade to break the ice, then the blade bends sideways, particularly if the blade is long. The use of such apparatus is thus to be avoided, particularly in high tension applications which require a long blade in order to provide isolation.
Another object of the invention is to provide a high tension apparatus that includes a blade of sufficient length to provide isolation and in which ice is broken both on opening and on closing without any danger of damaging the blade.